Trigger assembly for a spray gun

ABSTRACT

In a spray gun or the like having a valve held in closed position under fluid pressure and a trigger for opening the valve, a lever is pivotally connected to the trigger at one end, abutted against a stop at the other end, and provided with an arcuate intermediate portion in direct engagement with the valve opening rod or stem to provide a compound lever action to facilitate opening the valve against the fluid pressure. The trigger also includes a flanged portion that is slightly spaced from the lever in valve closed position, but brought into engagement with the lever after initially opening the valve against high pressure and after the pressure has equalized, so that the trigger then assumes a conventional relationship and feel relative to the valve. The mechanism is particularly useful in guns which dispense viscous materials and have large valve surfaces, wherein the force required to initially open the valve is considerable. The trigger assembly also incorporates a safety device for the operator&#39;&#39;s protection.

United States Patent Krohn TRIGGER ASSEMBLY FOR A SPRAY GUN Inventor:Duane D. Krohn, Arvada, Colo.

Binks Manufacturing Company, Franklin Park, Ill.

Filed: Aug. 1, 1973 Appl. No.: 384,687

Assignee:

References Cited UNITED STATES PATENTS 8/l934 Carr et al 239/526 5/1960Nord et al 239/569 X Primary ExaminerRobert S. Ward, Jr. Attorney,Agent, or FirmGray, Juettner, Pigott & Cullinan 51 Sept. 17, 1974 [57]ABSTRACT In a spray gun or the like having a valve held in closedposition under fluid pressure and a trigger for opening the valve, alever is pivotally connected to the trigger at one end, abutted againsta stop at the other end, and provided with an arcuate intermediateportion in direct engagement with the valve opening rod or stem toprovide a compound lever action to facilitate opening the valve againstthe fluid pressure. The trigger also includes a flanged portion that isslightly spaced from the lever in valve closed position, but broughtinto engagement with the lever after initially opening the valve againsthigh pressure and after the pressure has equalized, so that the triggerthen assumes a conventional relationship and feel relative to the valve.The mechanism is particularly useful in guns which dispense viscousmaterials and have large valve surfaces, wherein the force required toinitially open the valve is considerable.

The trigger assembly also incorporates a safety device for the operatorsprotection.

6 Claims, 3 Drawing Figures 1 TRIGGER ASSEMBLY FOR A SPRAY GUNBACKGROUND OF THE INVENTION This invention relates to a triggermechanism for opening a valve in a pressurized dispensing apparatus, andmore particularly to an improvement imparting substantial mechanicaladvantage to the trigger in its initial movement as the valve is beingopened against peak pressure in the gun.

In so-called airless or hydraulic spray guns, material is atomized byvirtue of passage through a specially designed nozzle or spray tip underhigh fluid pressure, in the order of 1,000 psi or higher. Passage of thematerial to the nozzle is conventionally under control of a valve, anddepending upon valve design, the fluid pressure in the gun acting uponthe closed valve may have to be overcome before the valve can be opened.With relatively small valves and/or relatively low fluid pressures, thevalve can be operated by a trigger pivotally mounted on the gun andconnected to the valve stem. A conventional gun typically includes abody with a rigid handle, and a trigger pivotally connected at its upperend to the body and depending therefrom forwardly of the handle, so theoperator can squeeze the trigger toward the handle and pull the valveopen. A return spring is provided to return the valve and trigger toclosed position upon release of the trigger.

The simple trigger mechanism above-described poses serious shortcomingsin guns in which the fluid pressure acting against the closed valve isvery high, i.e., wherein the combination of the area of the valveexposed to the fluid and the fluid pressure is such as to generate alarge force holding the valve closed. This is especially true when thematerial to be sprayed is highly viscous or dense, because such materialrequires both a large size valve opening and high pressure. Ai'rlessguns for dispensing highly viscous or dense materials, such as mastic,require large internal passages, a large outlet valve and high fluidpressure, all of which combine to greatly increase the pressure on theclosed valve and the force initially required to open the valve.Considerable extra force must be exerted on the valve initially tounseat the valve and permit pressure equalization around the valve.While a strong man might unseat the valve once or twice in aconventional application, he would quickly become fatigued and unable tooperate the gun with the frequency of valve opening and closingmovements conventionally required in spraying techniques.

SUMMARY OF THE INVENTION The present invention overcomes the aboveproblems by increasing the mechanical leverage of the trigger withoutincreasing the dimensions of the trigger or of the gun. An intermediateportion of the trigger carries a lever which is pivotally connected atone end to the trigger and has an intermediate portion abutting thevalve stem for opening the valve. The second end of the lever is freebut engages a stop extending from the gun body, which prevents movementof that end in a direction opposite to that of the trigger, thereby todefine a fulcrum for the lever.

As the trigger is squeezed, the lever is caused to swing about itsfulcrum so that said intermediate portion is urged against the valvestem as a compound or double lever affording substantial mechanicaladvantage.

, Thus, the valve is quite easily cracked open, so that the fluidpressure is equalized around the valve and this pressure is relieved oreliminated as a factor effecting valve movement. After the initialinternal pressure has been overcome, by movement of the trigger througha short are, conventional trigger action or feel is preferably restored.This is accomplished by causing a flange on the trigger to swing intoengagement with the lever and move the lever conjointly with thetrigger, whereby the trigger operates in a conventional manner relativeto the valve and the valve spring.

A safety feature is provided by mounting that part of the valve stemwhich is engaged by the lever for rotary movement and so shaping saidpart that it may be rotated into and out of engagement with the lever,whereby the trigger and lever assembly may be rendered operative orinoperative at the operators selection.

THE DRAWINGS FIG. 1 is a side view, partly in elevation and partly invertical section, of an airless spray gun incorporating the features ofthe present invention, the gun being shown with the valve thereof inclosed position;

FIG. 2 is a fragmentary view of the gun, showing the valve thereof in apartly open position; and

FIG. 3 is a sectional view taken substantially on line 33 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The airless or hydraulic gunshown in FIG. 1 generally comprises a solid body 10 having a downwardlydepending handle 12 at one end thereof and valved head assembly 14 atthe other end. A material inlet 16 is connected to a longitudinalpassage 18 within the head assembly, and said inlet may be connected bya pipe 19 to a remote inlet 20 at the base of the handle 12.

An apertured valve seat 22 is secured at the forward end of the passage18 by means of an internally threaded and apertured cap 24. Aninternally threaded nozzle cap 26 is fitted over the end of the headassembly with a gasket 28 interposed therebetween, said nozzle caphaving a central orifice 29 therein for reception of a spray tip (notshown) through which material is emitted under pressure when the valveis opened.

A rod or stem 30 is disposed axially in the passage 18 and has anenlarged round terminus or ball 32 at its forward end sealinglyengageable with the apertured valve seat 22. The other end of the rod 30extends through a suitable gland assembly 34 at the rear end of thepassage 18 adjacent the inlet 16, said gland assembly including anadjustable pressure fitting 36. The rod 30 is axially movable to openand close the valve, while the gland assembly 34 prevents leakage ofpressurized material around the rod toward the rear at all times.

The rear portion of the body of the gun is provided with a cylindricalchamber 38 coaxial with passage 30, and has a stem 40 slidably androtatably disposed therein, the forward portion 42 of saidstem extendingforwardly toward the rod 30 and out of the body of the gun. A helicalcompression spring 43 is disposed between a retainer 45 in the rear ofthe gun and a shoulder 44 on the stem 40, that portion of the stemcoextensive with the spring being of reduced diameter. The

stem 40 extends rearwardly to the exterior of the gun through an openingin the retainer 45 and is connected by a screw 47 to a safety lock knob46.

The forward portion 42 of the stem 40 is threaded and receives aninternally threaded collar 48 having a confined axial opening in theforward end which receives the rear end of the rod 30. The rear end ofrod 30 has a terminus 50 that is larger than the collar aperture, suchthat the rod is pulled by rearward movement of the collar and stem.

The stem 40 and associated rod 30 are moved rearwardly to open the valveby means of a trigger assembly including a main trigger 52 hinged at itsupper end to the gun body at 53 and depending downwardly therefrom.Movement of the trigger assembly toward the handle 12 causes the stem 40and rod 30 to move rearwardly, thereby moving the valve ball 32 awayfrom the valve seat 22 to open the passage between the pressurized inlet16 and the outlet 29 of the gun, as shown in FIG. 2. When rearwardpressure on the trigger 52 is released, the compression spring 43 urgesthe stem 40 and rod 30 forward to close the valve.

In the embodiment shown, the inlet 16, passage 18, valve seat 22 andvalve ball 32 are relatively large to accommodate dispensing ofrelatively heavy or viscous materials, such as glue, mastic and similarmaterials. The material to be dispensed must be introduced under highpressure through the inlet 16 to achieve proper and continuous flow, andthe pressure acting against the rearwardly exposed surfaces of the ballcreate a very considerable force holding the valve closed. In order toopen the valve, a pulling force must be exerted on the rod 30 which issufficient to overcome the internal pressure within the passage 18acting on the surfaces of the ball 32 exposed to the fluid. Under theseconditions, the use of a simple trigger to urge the stem 40 rearwardlydoes not provide sufficient leverage to facilitate opening of the valve.An operator may overcome the resistance to movement a few times butrepeated closing and opening of the valve will quickly result inoperator fatigue.

In accordance with the present invention, a compound lever arrangementis provided to assist the operator in effecting the initial stage ofvalve movement, i.e., during the first several degrees of movement ofthe trigger when the seal of the valve is broken. After the seal hasbeen broken and the internal pressure equalized on the valve ball 32, sothat the only pressure to be overcome is that of the spring 43, the loadis gradually transferred solely to the trigger 52 as it continues tomove rearwardly. The operator thereupon is afforded the normal orconventional feel of the trigger during spraying, but is materiallyassisted in getting the valve open.

As best shown in FIGS. 2 and 3, the upper end of the trigger 52 isbifurcated to define respective arms.54 and 56 which straddle the gunbody and extend downward with the rear edges of the arms approximatelyjuxtaposed to the front end42 of the stem 40. A pair of levers or plates58 and 60 (FIG. 3) are pivotally connected at their upper ends byrespective coaxial pins 62 to the respective anns 54 and 56 in parallelrelationship, said plates each having arcuate rear edge surfaces 64engageable in the direction of valve opening movement with the frontface of the stem end 42. The lower ends of the plates 58 and 60 areconnected together by a pin 68, such that the plates may swing togetherbetween the armsof the trigger on the common axis of their respectivepivots 62. The plates are thus mounted to be swingable in parallelvertical planes which are parallel to the axis of the rod 30,

A stop in the form of a threaded lock bolt having an enlarged head 72extends generally forwardly from the gun handle 12 with the shoulderbetween the shank and the head of the bolt being engageable by the lowerpin 68. This bolt is adjustable to vary the portion of the triggermovement within which the plates 58-60 will operate as a separate lever,as will subsequently appear. The trigger has a pair of inwardly facingand opposed flanges 74 and 76 engageable with straight forward edgesurfaces of the respective plates 58 and 60. As

shown in FIGS. 1 and 2, respectively, said flanges and forward edgesurfaces diverge downwardly away from one another when the trigger 52 isin the valve closed position, and engage flush against one another inthe valve open position.

In order to open the valve, the trigger 52 is squeezed toward thehandle. As the trigger moves rearwardly, the upper pivot pins 62 of theplate assembly 58-60 move rearwardly causing the arcuate rear edges 64of the plates 58 to 60 to push rearwardly against the front face of thestem end 42 and the attached pin 68 to be urged forwardly intoengagement with the fixed stop 72. The stop 72 thus becomes the fulcrumand the pins 62 the point of force application to constitute the plates58-60 a lever of the second class. Continued squeezing of the triggercauses rotation of the plates to the rear around the fulcrum formed bythe stop so that the arcuate surfaces 64 move rearwardly relative totheir initial position and urge the stem 40 rearwardly. Thus, thetrigger 52 and the assembly of the plates 58 and 60 cooperate to form acompound lever and provide an initial force multiplier to facilitateinitial opening of the valve.

In addition, the arcuate surfaces 64 of the lever assembly 5860 ride uprelative to their areas of engagement on the stem end 43 to serve as acam further contributing to the force multiplication provided by thelever.

Thus, during the first few degrees of rearward arcuate movement of thetrigger 52, there exists a compound lever and cam action affordingsubstantial mechanical advantage in getting the valve ball 32 off itsseat 22. The degrees of arcuate movement during which this conditionexists is adjustable by virtue of adjustment of the stop 72. All that isrequired is sufficient movement to crack the valve open, because fluidpressure will then equalize around the ball and the only resistance tofurther valve movement in the opening direction is that of the valvespring 43, which is a conventional and accepted condition in the spraygun art. In fact, spray gun operators rely on this spring pressure togive them so-called trigger feel to aid in their spraying techniques.Consequently, once the valve ball is off its seat, it is desirable toreturn to a conventional trigger-valve relationship.

According to the invention, this is accomplished by so correlating thetrigger to the lever assembly that there is a progressive decrease inthe distance between the trigger flanges 74-76 and the forward surfacesof the plates 58-60, so that the flanges eventually contact flushagainst the forward plate surfaces and restore the conventionaltrigger-valve relationship for continued rearward movement of the valveto full open position as shown in FIG. 2. When the trigger is released,the return spring 43 serves to return the trigger assembly and the valveto their original closed positions.

In summary, the trigger assembly includes a lever 58-60 of the secondclass which is disposed between the trigger 52, the fixed stop 72 andthe valve stem 40 to gain the extra mechanical advantage required toopen the valve. After the initial internal pressure resistance has beenovercome, the secondary lever is no longer required and becomesinoperative, with the force of the trigger being exerted directly on thevalve stem. Because of the arrangement, the gun is easy to use andoperator fatigue is eliminated.

Also, the structural assembly is such as to provide, conveniently andeconomically, a safety device for the operators protection. Because ofthe high fluid pressure required to achieve atomization in airless sprayguns, care must be exercised to insure that the material emanating fromthe gun does not strike anyone, as serious physical injury could beimposed. This is especially true of the operator. Thus, it is desired torender the trigger inoperative, i.e., either to lock it in closedposition or to disconnect it from the valve stem, when the gun is not inactive, supervised use. According to the invention this is accomplishedby mounting the stem 40 for rotation by the external knob 46 and cuttingaway diametrically opposed portions 66 of the stem end 42 so that thestem can be rotated 90 between the operative position shown in FIG. 3and an inoperative position wherein the stem end 42 is of a width lessthan the spacing between the lever plates 58-60 so that the plates clearthe stem and cannot engage and move the same. Thus, in the inoperativeposition, the trigger hangs free and cannot operate the valve, wherebythe operator may safely lay the gun down or hang it up during his restperiods and may clean the gun or change the spray tips without fear ofinadvertently opening the valve and injuring himself.

What is claimed is:

1. In a trigger assembly for a spray gun having valve means held inclosed position under fluid pressure, the improvement comprising atrigger pivotally connected to the spray gun, a lever pivotallyconnected to said trigger and having a portion engageable with saidvalve means, and stop means on the spray gun engageable by said leverfor providing a fulcrum for said lever, said trigger being movable invalve opening direction to urge said lever against said valve means withcompound leverage to move said valve means toward valve open position.

2. In the trigger assembly of claim 1, said trigger being pivotallyconnected at its upper end to the gun and depending therefrom forrearward movement to open the valve means, said lever being pivotallyconnected at its upper end to said trigger and having a rearwardlyprotruding intermediate portion engageable with said valve means, saidstop means being enageable with a forwardly facing portion of said leverat the lower end thereof whereby said lever comprises a lever of thesecond class.

3. In the trigger assembly of claim 2, said trigger including a flangenear the forward edge thereof spaced from said lever in valve closedposition and engageable with said lever after predetermined movement invalve opening direction to cause said lever to move con- 7 jointly withsaid trigger.

4. In the assembly of claim 3, said stop means having a head at the endthereof disposed forwardly of the lower end of said lever and engageablewith said lever to define the fulcrum therefor, said stop means beingadjustable to vary the degree of movement of said trigger prior toengagement of said flange with said lever.

5. In the assembly of claim 2, said trigger being bifurcated at itsupper end to form a pair of arms, said lever being mounted between saidarms and comprising a pair of plates pivotally mounted at their upperends in parallel on respective arms and a pin extending between andconnecting the lower ends of said plates, said pin being engageable withsaid stop.

6. In the assembly of claim 5, said valve means including a stemextending between said plates and a rotatable stem member having a firstposition in which forwardly facing surfaces thereof are juxtaposed tosaid plates and a second position wherein said surfaces are disposedbetween said plates, and means for rotating said stem member betweensaid positions.

1. In a trigger assembly for a spray gun having valve means held inclosed position under fluid pressure, the improvement comprising atrigger pivotally connected to the spray gun, a lever pivotallyconnected to said trigger and having a portion engageable with saidvalve means, and stop means on the spray gun engageable by said leverfor providing a fulcrum for said lever, said trigger being movable invalve opening direction to urge said lever against said valve means withcompound leverage to move said valve means toward valve open position.2. In the trigger assembly of claim 1, said trigger being pivotallyconnected at its upper end to the gun and depending therefrom forrearward movement to open the valve means, said lever being pivotallyconnected at its upper end to said trigger and having a rearwardlyprotruding intermediate portion engageable with said valve means, saidstop means being enageable with a forwardly facing portion of said leverat the lower end thereof whereby said lever comprises a lever of thesecond class.
 3. In the trigger assembly of claim 2, said triggerincluding a flange near the forward edge thereof spaced from said leverin valve closed position and engageable with said lever afterpredetermined movement in valve opening direction to cause said lever tomove conjointly with said trigger.
 4. In the assembly of claim 3, saidstop means having a head at the end thereof disposed forwardly of thelower end of said lever and engageable with said lever to define thefulcrum therefor, said stop means being adjustable to vary the degree ofmovement of said trigger prior to engagement of said flange with saidlever.
 5. In the assembly of claim 2, said trigger being bifurcated atits upper end to form a pair of arms, said lever being mounted betweensaid arms and comprising a pair of plates pivotally mounted at theirupper ends in parallel on respective arms and a pin extending betweenand connecting the lower ends of said plates, said pin being engageablewith said stop.
 6. In the assembly of claim 5, said valve meansincluding a stem extending between said plates and a rotatable stemmember having a first position in which forwardly facing surfacesthereof are juxtaposed to said plates and a second position wherein saidsurfaces are disposed between said plates, and means for rotating saidstem member between said positions.